Method for manufacturing printed circuit board having different thicknesses in different areas

ABSTRACT

A method for manufacturing a printed circuit board (PCB) having different thicknesses in different areas includes: providing a first substrate having two lateral unwanted portions bounded two imaginary boundary lines, a binder layer having a through opening and a second substrate having a mounting area for mounting electronic elements; forming two slots bounded the imaginary boundary lines in an intermediated unwanted portion of the first substrate corresponding to the mounting area; laminating the first and second substrates, and the binder layer with the mounting area exposed via the through opening; filling the two slots and the through opening with a filling material, thereby obtaining a semifinished PCB board; cutting the semifinished PCB board along the imaginary boundary lines to remove the two lateral unwanted portions and a portion of the second substrate corresponding to the two lateral unwanted portions; and removing the intermediate unwanted portion and the filling material.

BACKGROUND

1. Technical Field

The present invention generally relates to printed circuit boards, andparticularly relates to a process for manufacturing a printed circuitboard having different thicknesses in different areas.

2. Discussion of Related Art

Printed circuit boards (PCBs) having different thicknesses in differentareas have been widely developed. The PCB usually includes differentplurality of layers in different areas, i.e., has a thick portion with anumber of layers and a thin portion with fewer layers. The thick portionhas a higher circuit density whilst the thin portion exhibits higherflexibility.

FIG. 9 shows a structure of a PCB 100 having different thicknesses indifferent areas. The PCB 100 includes a first substrate 110, a binderlayer 130 and a second substrate 120. The PCB 100 has an opening 101passing through the second substrate 110 and the binder layer 130. Thefirst substrate 110 has an electrical traces layer 111. A mounting area112 of the electrical traces layer 111 for mounting electronic elementsis exposed via the opening 101.

FIGS. 10˜11 show a process for manufacturing the PCB 100. As shown inFIGS. 10˜11, a first substrate 110 including an electrical traces layer111, an binder layer 130 having an opening 131 and a second substrate120 are provided. The second substrate 120 includes a base 121 and aconductive layer 122 formed on the base 121. As shown in FIG. 11, thesecond substrate 120, the binder layer 130 and the first substrate 110are laminated, and a portion 120 a of the second substrate 120corresponding to the opening 131 is removed using a laser cutter or amilling cutter.

When the base 121 is made of glass fibers and polymer resin, i.e., thesecond substrate 120 is a rigid, the second substrate 120 may havedifferent thickness in different areas. It is known that a cutting depthof a laser cutter is in direct proportion with a cutting energy of thelaser cutter. To cut off the portion 120 a without damaging the mountingarea 112, a cutting energy of the laser cutter must be adjustedaccording to a practical thickness of the second substrate 120 where thelaser is applied on. However, it is difficult to precisely control thecutting energy of the laser cutter. Thus, during cutting off the portion120 a, the mounting area 112 may subject to damages cause by the lasercutter.

What is desired, therefore, is a method for manufacturing a printedcircuit board having different thicknesses to overcome theabove-described problems.

SUMMARY

In one embodiment, a method for manufacturing a printed circuit boardhaving different thicknesses in different areas is provided. A firstsubstrate having two first lateral unwanted portions bounded twoimaginary boundary lines is provided. Two slots running between theimaginary boundary lines is defined in the first substrate, thus, thefirst substrate has an intermediate unwanted portions bounded by theslots and the imaginary boundary lines. A binder layer having a firstsurface, an opposing second surface and a through opening is provided.Two inner side surfaces in and at opposite sides of the through openingare defined. The first substrate is attached to the first surface of thebinder layer with the slots respectively aligned with the inner sidesurfaces. A second substrate having two second lateral unwanted portionsis provided. The second substrate is attached to the second surface ofthe binder layer with the second lateral unwanted portions respectivelyaligned with the first lateral unwanted portions. The through openingand the slots is filled using a filling material thereby obtaining asemifinished PCB board. The semi-finished PCB board is cut along theimaginary boundary lines to remove the first and second lateral unwantedportions. And the intermediate unwanted portion and the filling materialare removed.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the embodiments can be better understood with referenceto the following drawings. The components in the drawings are notnecessarily drawn to scale, the emphasis instead being placed uponclearly illustrating the principles of embodiments. Moreover, in thedrawings, like reference numerals designate corresponding partsthroughout the different views.

FIG. 1 is an exploded, isometric view of a first substrate, a secondsubstrate and a binder layer having a through opening according to anexemplary embodiment.

FIG. 2 is similar to FIG. 1, but showing a first slot and a second slotdefined in the second substrate.

FIG. 3 is an isometric view of a combination of the first substrate, thesecond substrate and the binder layer.

FIG. 4 is a cross sectional view of the semi-finished PCB of FIG. 3,taken along line V-V thereof.

FIG. 5 is similar to FIG. 4, but showing a semifinished PCB board withprotective layer filled in the first slot, the second slot and thethrough opening.

FIG. 6 shows the semi-finished PCB of the FIG. 5 with unwanted portionsthereof being removed.

FIG. 7 is a cross-sectional view of the semi-finished PCB of the FIG. 6,taken along line VIII-VIII, showing a step of removing the protectivelayer.

FIG. 8 is an isometric view showing a printed circuit board havingdifferent thicknesses in different areas.

FIG. 9 is a cross-sectional view of a typical printed circuit boardhaving different thicknesses in different areas.

FIGS. 10˜11 are cross-section views showing a process for manufacturinga typical printed circuit board as shown in FIG. 9.

DETAILED DESCRIPTION OF EMBODIMENTS

An exemplary method for manufacturing a printed circuit board (PCB)having different thicknesses in different areas, comprising the steps inno particular order of:

-   -   providing a first substrate, the first substrate having two        first lateral unwanted portions bounded two imaginary boundary        lines,    -   defining two slots in the first substrate, the slots running        between the imaginary boundary lines, the first substrate having        an intermediate unwanted portions bounded by the slots and the        imaginary boundary lines;    -   providing a binder layer having a first surface and an opposite        second surface, the binder layer having a through opening        defined therein, and two inner side surfaces in and at opposite        sides of the through opening;    -   attaching the first substrate to the first surface of the binder        layer with the slots respectively aligned with the inner side        surfaces;    -   providing a second substrate, the second substrate having two        second lateral unwanted portions;    -   attaching the second substrate to the second surface of the        binder layer with the second lateral unwanted portions        respectively aligned with the first lateral unwanted portions;    -   filling the through opening and the slots using a filling        material thereby obtaining a semifinished PCB board;    -   cutting the semi-finished PCB board along the imaginary boundary        lines to remove the first and second lateral unwanted portions;        and    -   removing the intermediate unwanted portion and the filling        material.

The first and second substrate, and the binder layer can be providedsimultaneously. The first and second substrate can be simultaneouslyattached onto the first and second surfaces of the binder layer as well.

The method for manufacturing a printed circuit board having differentthicknesses in different areas will be discussed in detail with thefollowing exemplary embodiments.

As shown in FIG. 1, a first substrate 300, a second substrate 200 and abinder layer 400 are provided.

The first substrate 300 is rigid, and includes a first base 310 and aconductive layer 320 formed thereon. The conductive layer 320 has anouter surface 302. The first base 310 may be a single layer structurecomprised of a dielectric resin and glass fibers, or a multilayerstructure including a plurality of the mentioned single layer and aplurality of conductive layers. In the present embodiment, the secondbase 310 is a single layer structure comprised of dielectric resin andglass fibers. The first substrate 300 has a first portion 303, a secondportion 304 and an intermediate portion 305 between the first portion303 and the second portion 304. The intermediate portion 305 has twofirst lateral unwanted portions 306 bounded a first and second imaginaryboundary lines 3071, 3072 defined in the outer surface 302 and anintermediated unwanted portion 307 between the two first lateralunwanted portions 306. The first and second imaginary boundary lines3071, 3072 are parallel to each other.

The second substrate 200 includes a second base 210 and two electricaltrace layers 220 formed on opposite surfaces of the second base 210. Thesecond base 210 may be a single layer structure of dielectric resin or acombination of dielectric resin and glass fibers, or a multilayerstructure comprising a plurality of the mention single layer mentionedand a plurality of conductive layers. i.e., the second substrate 200 canbe a flexible PCB substrate or a rigid PCB substrate. In the presentembodiment, the second substrate 200 is flexible. The electrical traceslayer 220 has two second lateral unwanted portions 222 and a mountingarea 221 defined between the two second lateral unwanted portions 222.The two second lateral unwanted portions 222 are corresponding to thetwo first lateral unwanted portions 306. The mounting area 221 iscorresponding to the intermediated unwanted portion 307 and isconfigured for mounting electronic elements. In the illustratedembodiment, the mounting area 221 is located at an intermediated regionof the electrical traces layer 220.

The binder layer 400 has a first surface 401 and an opposite secondsurface 402, and defines a through opening 410 therein. Thereby, thebinder layer 400 has a first inner side surface 421 and an oppositesecond inner side surface 431 in the opening 410. A distance between thefirst inner side surface 421 and the second inner side surface 431spatially corresponds to a width of the mounting area 221, so that themounting area 221 can be entirely exposed via the opening 41 0. Thebinder layer 400 is used for conglutinating the first substrate 200 andthe second substrate 300.

The dielectric resin and the binder layer 400 can be made of a materialselected from the group consisting of polyimide,polytetrafluoroethylene, polythiamine, polymethacrylic acid,polycarbonate, polycarbonate ester, polyester, and copolymer of imide,ethylene and dimethyl terephthate. The conductive layer 320 and theelectrical traces 220 can be comprised of copper, silver or aluminum.

As shown in FIG. 2, a first slot 3023 and a second slot 3024 are formedin opposite ends of the intermediated unwanted portion 307 that bothperpendicular adjoining to the first imagery boundary 3071 and thesecond imagery boundary 3072. The first and second slot 3023, 3024 passthrough two opposite surfaces of the first substrate 300, and areparallel to each other. The first slot 3023 and the second slot 3024 maybe formed by stamping or laser ablating. In the present embodiment, thefirst slot 3023 and the second slot 3024 are formed using a stampingprocess.

As shown in FIGS. 3˜4, the first substrate 300 is attached onto thefirst surface 401 of the binder layer 400 with the first and secondslots 3071, 3072 respectively aligned with the first and second innerside surfaces 421, 431. The electrical trace layers 220 of the secondsubstrate 200 is attached onto the second surface 402 of the binderlayer 400 with the second lateral unwanted portions (not shown) alignedwith the first lateral unwanted portions 306.

As shown in FIGS. 4˜5, a filling material is filled into the first slot3023, the second slot 3024 and the through opening 410, therebyobtaining a semifinished PCB board 700 having a protective layer 500formed therein. As such, liquid such as etchant can't seep into themounting area 221 via the first and second slots 3023, 3024. Therefore,electrical traces 220 in the mounting area 221 are protected fromcorrosion. The protective layer 500 is made of binder can be easilyremoved after solidification, such as ultraviolet solidification. Thefilling material can be filled into the first slot 3023 and the secondslot 3024 using a printing method or an injecting process, and thensolidified.

As shown in FIG. 6, the first lateral unwanted portion (not shown) andthe second lateral unwanted portion (not shown) are removed using acutting method or a stamping process. Referring to FIG. 1 and FIG. 5,the first and second lateral unwanted portion 306, 222 are cut along thefirst and second imaginary boundary lines 3071, 3072, thus, theintermediated unwanted portion 307 is separated from the first portion303 and the second portion 304 via the protective layer 500.

As shown in FIGS. 7˜8, the intermediated unwanted portion 307 and theprotective layer 500 are removed, thus obtaining a printed circuit board600 having different thicknesses in different areas. A plurality ofelectrical traces could be formed in the first portion 303 and thesecond portion 304.

In the present embodiment, before laminating the first substrate 200,the binder layer 400 and the second substrate 300, a first slot 3023 anda second silt 3024 are preformed in the intermediated unwanted portion307. And after laminating, the two slots 3023, 3024 are aligned with thefirst and second inner side surfaces 421, 431, and the mounting area 221is exposed via the through opening 410. As such, a protective layer 500could be formed on the mounting area 221 via the two slots 3023, 3024 toprotect the mounting area 221 from corrosion, and a cutting could bedone along the boundaries of the intermediated unwanted portion 307. Asa result, the intermediated unwanted portion 307 could be removedwithout cutting, therefore, the mounting area 221 is protected frombeing damaged.

While certain embodiments have been described and exemplified above,various other embodiments will be apparent to those skilled in the artfrom the foregoing disclosure. The present invention is not limited tothe particular embodiments described and exemplified but is capable ofconsiderable variation and modification without departure from the scopeof the appended claims.

1. A method for manufacturing a printed circuit board (PCB) havingdifferent thicknesses in different areas, comprising: providing a firstsubstrate, the first substrate having two first lateral unwantedportions bounded two imaginary boundary lines, defining two slots in thefirst substrate, the slots running between the imaginary boundary lines,the first substrate having an intermediate unwanted portions bounded bythe slots and the imaginary boundary lines; providing a binder layerhaving a first surface and an opposite second surface, the binder layerhaving a through opening defined therein, and two inner side surfaces inand at opposite sides of the through opening; attaching the firstsubstrate to the first surface of the binder layer with the slotsrespectively aligned with the inner side surfaces of the binder layer;providing a second substrate, the second substrate having two secondlateral unwanted portions; attaching the second substrate to the secondsurface of the binder layer with the second lateral unwanted portionsrespectively aligned with the first lateral unwanted portions; fillingthe through opening and the slots using a filling material therebyobtaining a semifinished PCB board; cutting the semi-finished PCB boardalong the imaginary boundary lines to remove the first and secondlateral unwanted portions; and removing the intermediate unwantedportion and the filling material.
 2. The method as claimed in claim 1,further comprising forming electrical traces in the second substrateafter removing intermediate unwanted portion and the filling material.3. The method as claimed in claim 1, wherein the first substrate is arigid PCB substrate, and the second substrate is a flexible PCBsubstrate or a rigid PCB substrates.
 4. The method as claimed in claim1, wherein the slots are parallel to each other.
 5. The method asclaimed in claim 1, wherein the slots are perpendicular to the imaginaryboundary lines.
 6. The method as claimed in claim 1, wherein theimaginary boundary lines are parallel to each other.